5. The drawing shown below represents part of the arrangement of blood vessels i
ID: 3478534 • Letter: 5
Question
5. The drawing shown below represents part of the arrangement of blood vessels in the kidney. The arrangement includes 2 sets of resistance vessels (afferent and efferent arterioles (aff art and eff art) separated by a capillary bed, the glomerulus (glom): RRAalvein = 3 mm Hg Raff art= 0.012 mmHg·min/ml Retart0.003 mmHg·min/ml ProRal art = 63 mm Hg Ralo 222 Assume = 1 for kidney capillaries, disregard K for the following calculations. Raon ??? Pint glom At = 1 mm Hg = 12 mm Hg 0 mm Hg a) Calculate Raoo b) Calculate flux (J) through the glomerular capillary bed. Is there net filtration or reabsorption in this capillary bed? c) If the efferent arteriole is dilated, such that Retart-0.001, what is the new value for Ralon? With Retart-0.001, calculate the new flux (J) through the glomerular capillary bed. Is there net filtration or reabsorption in this capillary bed?Explanation / Answer
a) As pressure and resistance for afferent and efferent artrioles is given therefore we can find pressure of glomerular capillary by using following formula
Pglom= [(Reff art/Raff art ) Paff art X Peff art] / 1 + (Reff art/Raff art)
Adding all the values provided in the question in above formula
= [(0.003/0.012) 63 + 3] / [1+ (0.003/0.012)]
= [(0.25) 63 + 3] / [1+0.25]
=18.75/1.25
=15
Therefore, PGlom= 15mmHg
b) In order to find J, we need to all the values in the formula given in the question
J = (15-1) - 1 (12-0), where PGlom= 15mmHg, Pint= 1mmHg, sigma=1
therefore J= 14 - 1 (12)
= 14-12
= 2
As the value of J is positive 2 therefore there is net filtrationin this capillary bed
c) Now if Reff art = 0.001, then we can find Pglom by putting all the values in
Pglom= [(Reff art/Raff art ) Paff art X Peff art] / 1 + (Reff art/Raff art)
= [(0.001/0.012) 63 + 3] / [1+ (0.001/0.012)]
= [(0.083) 63 + 3]/ [1+0.083]
=8.25/1.083
=7.61
Therefore new value of Pglom= 7.61 mmHg
d) To find new value of J we will put new value of Pglom in the formula given in the question:
J= (7.61-1) - 1 (12-0)
=6.61-12
= - 5.39
As the value of J is negative 5.39 therefore there is rebsorption this capillary bed.
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